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A. D. KARR ET AL METHOD AND APPARQPUS FOR CONDITIONING AIR April 18, 1933.

Filed April 7, 1931 'Patented Apr. v*1.8.1933

UNITED STATES vPirrEN'r OFFICE ALFRED D. KARB, 0F NEWARK, NEW JERSEY, AND KARL I). PmKJNS, 0F .NEW YORK, N. ASSIGNRS T0 AUDIFFR-EN REFRIGERATING MACHINE COMPANY, OF NEW YORK, N. Y., A. CORPORATIQN UF NEW JERSEY l c METHOD AND AIIFABATUS FOR- CONDITIONING AIB vApplication led April '1,v 19.31. Serial No'. 528,340.

This invention relates to th'e conditioning of air and more particularly concerns an improved method of and apparatus'for maintaining Ldesirable atmospheric conditionsI Within rooms, buildings 'or otherenclosures. In maintaining healthful and comfortable air conditions in large public enclosures such as theaters, auditoriums, etc., it is necessaryL particularly during the warmer seasons of the year, to cool and dehumidify the air sup-I plied to the enclosure. Dehumidication involves cooling the air to a temperature below its dewpoint whereby some of the moisture contained in the air is condensed and removed lreheat the air after dehumidification and before it is introduced to the enclosure. The cooling and subse uent reheating of the air involves considera le expense and in many cases makes the cost ofy proper air conditioning prohibitive.

The conditioning of air for use in enclosures usually involves not only the treatment and introduction of fresh air from outside of the enclosure, but also the reintroduction and recirculation ofair from the enclosure, the recirculated air being treated to de humidity the same before reint-roduction.

' With the above and other considrations in mind, it is ,proposed in'accordance with the present invention to provide an improved and simplified method for maintaining the air in an enclosure in the proper condition as to temperature and humidity which method effects a considerable saving in the amount of energy expended for the dehumidication and subsequent reheating of the'air. More specifically, the improved method of our in'- vention involves supplying both fresh andv recirculated air to the enclosure, this air being first treated in such a manner that some of the heat content of both the 4fresh outside air and the air withdrawn from the enclosure is conserved and is employed to bring the dehumidiiied airfto the proper room temperature before it is reintroduced to the enclosure.

It is a further obiect of the invention provide an improved method of automatically controlling the temperature and humidity of the air in the enclosure.. Our invention includes not only an improved air conditioning method but also improved and simplified apparatus by means of which the method may be carried into e'ect. y

The above and other objects of our invention 'are carried out by'collecting all of the air to be introduced tothe enclosure in a single stream and subjecting such stream to contact with cooling units or heat absorbers whereby some of the air in the stream is -cooled and dehumidied by contact with the cooling units while other portions of the air Rr-ISSUED pass between the elements of and are aifected to a lesser degree bythe units and accordingly retain considerable heat which is returned to the cooled and dehumidified air before the air stream is introduced to the enclosure.v

The cooling unit-s employed preferably comprise a plurality ofseparate coils or cooler sections, each being located in the path of the air stream, and the supply of refrigerant or cooling Huid to the different units is pref? erably selectively controlled byV automatic means responsive to the atmospheric conditions within the enclosure. The air employed in .the stream to bev treated may comprise fresh outside air only, but it is usually preferred to use a mixture of fresh air and air withdrawn from the enclosure for this 'urpose. In this manner, a' portion of the eat' cooled and dehumidified portions of the air stream. Since only a portion of the air in 4the streamis dehumidied, the amount of energy expended vin refrigerating the air as? troduced to the enclosure by variation of thev number of active cooling units and by variation'of the temperature of the cooling medium circulated through -the active umts.- \The I number of active cooling units, that is, the

Aproportion of the a'ir in the stream which is Y dehumidified is preferably governed automatically in accordance with the humidity or the wet bulb temperature of the air Withdrawn from the renclosure for recirculation.

The above and other objects and char`- l .l5 Fig. 2 is a sectional view of the cooler chamber employed in the system of Fig. 1; and

Figs. 3, 4 and 5 areenlarged sectional views of the different types of automatically operable valves employed in the system of Fig. 1. 1 Referring to the drawing, and` more particularly to Fig. 1,.the system shown is employed to condition the air'in a room or enclosure represented at 7, and comprises generally a cooler W, a fan or equivalent propelling device 8 and an air'heating device H.

The cooler W includes a singleair chamber 9. The bottom portion of the chamber 9 forms a liquid collecting pan 12 which is preferably provided with a drain pipe 13 forl carrying off the moisture condensed from the air withinthe chamber. A plurality of eliminator lates or `baiiies 16 are provide near the discharge end of the chamber 9,

these plates being of any suitable form andl preferably comprising nested plates having angularly disposed surfaces. AL set of similar plates 17 is disposed across the inlet end v of the cooler chamber 9, the shape of the l plates being similar to that of theplates 16. 4 T'he plates 17 are preferably coated with a viscous fluid such as oil which maybe supplied to the plates through a valve controlled pipe 18 and nozzle 19. The oil falling from carriedoi'in the oil overflow pipe 21. The suction fan 8 is connected tothe discharge end of the cooler chamber 9 and delivers conditioned air to the room 7 through the duct 22.

The heater H may take any suitable form and preferably comprises a coil of pipe or finned radiator 23 disposed at the discharge end of the cooler chamber 9 beyond the eliminatorplates 16. Steam or any other suitable heatingfluidmaybeintroducedto the radiator 2 3Qthrough the pipe 24 under the'control of the valve 25 as hereinafter described, and an exhaust pipe .27 maybe employed to withdraw steam and moisture from the radiator. j Referring now more particularly to the cooling surfaces or units employed in the cooler W, inthe disclosed embodiment, these units take the form of a plurality of coil sections 10, 11, 14, 15 and 70, each of these sections being disposed across the cross section of the chamber 9, as clearly shown in Fig. 2.

the plates 17 is collected in the oil well 2O and constructed in cellular form, if desired. The

' coil lsections 10, 11., 14, 15 and 70 are respecsupply pipe 71 through the automatically operable valves 72, 73, 74, 75 and 76. Liquid is discharged from the coil sections 10, 11, 14, 15 and 70 through the pipe 31 which leads to the intake of a power driven pump 29.

Since the system is designed primarily to cool and dehumidify the air supplied to the enclosure, means arev provided for at times supplying refrigerated water or other liquid tothe coil sections of the cooler W. The cooling liquid is supplied to the coil sections by the pump 29 which withdraws liquid from the pipe 31- and returns this liquid either through a liquid cooler C or directly through the pipe 30 to the supply pipe 71. The proportion of Withdrawn liquid which is'passed through the cooler 'C is` controlled by means of a mixing valve 39 and the supply of liquid to the various coil sections of the cooler is governedby the means of valves 72 through 76 as hereinafter explained. It should be understoodA that the liquid passing through the cooler C is refrigerated by contact with the evaporator coils of a mechanical refrigeration system or in'any other suitable manner. Itis generally preferred to voperate the pump 29 at a constant speed and tovregulate the How of liquid to the coil sections by the valves 72 through 76. pressure in the pipes of the system, the pump employed may be provided with a bypass adapted to open when the liquid pressure reaches a predetermined high value or a pum-p of the iinpeller type may be used to provide a similar pressure limiting operation.

The various control devices and connections employed in the illustrated embodiment of the invention will now be described. The treatment of the air suppliedto the enclosure is preferably governed automatically in accordance with atmospheric conditions within the enclosure, and accordingly, the sensitive ele- Inorder`` to prevent excess liquid The coils of the sections may be provided with heat absorbing projections or may be iiof ments of a dry bulb thermostat 33and a wet'l bulb thermostat or hygrostat 34 are disposedV within the duct 35 through which air is withdrawn from the enclosure 7. Itis obvious that these sensitive elements might be -disposed within the enclosure 7, if desired.;

The dry bulb `thermostatr33 is of known construction and is suitably designed to control the flow of compressed air from a' source indicated by the pipe 36 to the' operating diaphragms of the valves 25 and 39 in accordance with temperature variations or the air in the duct 35. The thermostat 33 is preferably designed to supply compressedair at full pressure when the temperature ofthe air in the duct 35 is above a predetermined value,

to cut off the supply of such ,compressed air and vent the valve diaphragm chambers to also of known construction and is desi y ed to control the flow of compressed air rom the pipe 36 to the operating diaphragms of the control valves 72 through 76 in accordance with changes in the temperature of evaporation or relative humidity of the return air in high value,

4pressure on the duct 35. The wet bulb thermostat is preferably designed to supply compressed a1r at full pressure when the temperature of evaporation or relative humidity of they air in the duct is below the predetermined value for which the instrumentr set, to cut oil the supply of compressed air and -to vent thesel va ve diaphragmsy when the temperature o evaporation or humidity ofthe air isabove ,this predetermined value and to vary the air the valve diaphragms' from atmospheric pressure to full pressure as the temperature of evaporation or relative humidity of the air in value slightly bove to a value slightly below the predetermined valuey forwhch the instrument is set. l

A. pressur relief valve R is connected to the supply pipe 77 leading from the thermostat 33 to the valves 25 and 39. The relief valve R may take,` anysuit-able form and is designed in any desired manner to vent the control airV pipe 77 to the atmosphere if the pressure in this pipe rises. to an abnormally such as 14 lbs. per square inch, the

f valve being suitably designed to remain open rwhenonce opened by such pressure until the air pressurer in the pipe 77 has been reduced.' to say 7 lbs. per square inch.

One form of valve capable of operating in this manner has been shownin Fig.. 5.` The valve shown comprisesacasing 7 8 and a small cylinder 7 9v carrying a sliding piston 8O and a large cylinder 81 carrying a larger piston 82, the piston 80 and` 82 being rigidly connected bythe rod 83. A valve operating rod 84 having a valve gate 85 on the upper end thereof is fixed to the upper' surface of the small piston 80, and the gate 85 cooperates with a valve seat connected to the pipe 77. A vent port 86 permits thel escape of air from the pipe 77 to the atmosphere when the gate 85 is: lowered from its seat. The venting chamber 87 is sealed by a flexible diaphragm 89, and a duct 90 delivers airatv the pressure in the pipe 77 to the small cylinder 79. A

spring 91 normally holds the pistons 80 and 82l in their raised positions and thus maintains the valve gate 85 closed ony its; seat. In o ration, whenfthe air preure'in the pipe 7 reaches; an abnormally high value such as 14 lbs. per square inch,- thispressure, acting on thesmall pistonSO, is suilicient to over# the duct 35 changes from a* the valve gate 42 come the-"resistanceof the the l pistons 80 and 82 are depressed, t ereby openmg valve gate 85 and venting the pipe 77 to atmosphere through the port 86.` As soon as the piston 80 isV depressed, the air yfrom the upper cylinder 79 is admitted to theA lower cylinder 81 through the grooves 92 which are uncovered by the piston 80 in itsdescent. Since the piston 82 is of considerable greater area than is the piston 80, the 'valve gate 85 will be maintained open the air pressure in the pipe 77 has been` reduced to a considerably lower value than that to Y initially depress the small piston 80, and accordingly, the valve remains open until the air pressure in the pipe 77 and the cylinders 79 and 81 falls to say 7 lbs. per square inch. At this point,l the spring 91 raises the pistons and closes the valve.. r e

The operation of the valves 25 andwill be best understood by reference to Figs.'3 and 4 wherein these valves have been shown in detail. Fig. 4 is an enlarged sectional view of the mixing-valve 39` which controls the pere passing through the centage of cooling liquid cooler C. The inlet 30 of valve is` connected to the discharge of thepump 29 and governs the division of liquid between the pipe 43"leading to the cooler C and the pipe pipe 71". When the gate 42 is in the extreme upper" position as shown, all of the liquid passes through the pipe 43 and the cooler C,

and accordingly, the lowestl available liquid' temperature is obtained. With the gate 42 in the lowest position, all of the liquid. is by-passed around the cooler C through the pipe 41 and the temperature of the liquid rises to a maximum value dueto the heating of the liquid. by the air in the chambery 9. At

intermediate positions. of: the valve lgate 42,.'

intermediate liquid` temperatures are obtained, the valve gate 42 is operated by a flexible wardly by the springA 46., Thus.,A an increase in air pressure supplied tothe diaphragm 45 corresponding to an increase in. of the air in the duct 35 acts valve gate 42 and by-pass a greater amount of liquid around the cooler C whereby the liquid temperature is increased whereas a decreasein controlA air pressure corresponding to a. decreasen temperature of the returnl air permits the gate 42 to rise and supply a: greater amount ofV liquid vto the cooler C, whereby the liquid temperature is lowered.` In thespecific. embodiment of the invention herein described, the

, presures ofV 13 lbs.. persquare inch or'higher,

on its upper seat at pressures;l of 7 lbs.. pery square inch or lower. i The steamy valve 25 is' operated by a.4 direct 4l lendingto the supply diaphragm 45 which is biased up- 'u temperature to lower the spring 46 of the valve 39 is of such a. strength' that the gate ,closed on its lower seat at air acting diaphragm` and theI construction of' a 1li l 12s undisclosed' ,A

valve of this type is shown in Fig. 3. The valve gate 47 1s operated by a -iexible diaphragm 48 acting against the pressure of a spring 49, the spring acting to raise the gate and open the valve when the control air pressure on the diaphragm decreases below a pre- -determined value and the air pressure above a predetermined value acting to lower the gateand close the valve a ainst resistance of lthe spring. This type o valve is' also employed to control the ilow of cooling liquid to the coil sections 10, 11, 14, 15 and 70 and accordingly, the illustration in Fig. 3 is rep-v resentative not only of the. steam valve but also of the liquid valves 72 through 76. In the specific embodimentof the invention herein described, the steam lvalve 25 is assumed to be closed at pressures of 6 lbsl per square inch or higher an'd open at atmos-l pheric pressure. The valve7 2 is assumed to close at 14 lbs. pressure or higher and open at 12 lbs. pressure or lower, thevalve 73 is A assumed to close at 12 lbs. pressure or higher and open at 10 lbs. pressure or lower, the valve 7 4 isassumed to close at 10 lbs. pressure Aor higher and open' at 8 lbs. pressure or lower,

the valve 75 is assumed to close at 8 lbs. pressure or higher and open at 6 lbs. pressureor lower, and the valve 76 is assumed to close at 6 lbs. pressure or higher and open at 4 lbs. pressure or lower.

The liquid employed in the system is preff erably water, but it is sometimes preferred to employ a cooling liquid having a lower freezing temperature or a higher vaporizing y temperature than ,water or one having both of thesechar'acteristic's. Thus, liquids such as brine solutions or ethylene gl col either in solution with water or in the anli'ydrous state may be used.

n operating .the illustrated embodiment ,of our improved air conditioning system,

fresh air from y'outside of the enclosure is drawn 1n through the duct 60 and'is mixed with return air from the enclosure delivered through the duct 35. All of the mixed fresh 'and used air then enters the chamber 9 through the oil coated plates 17, and foreign ,bodies such as dust, lint, etc., are removed from the air at this point. The passage. of the air through the plates 17 also serves -to remove eddys from the air currents so that the air Hows smoothly and uniformly through the chamber 9. Thefresh and recirculated air passes through the chamber 9, preferably at a constant velocity,between the various rtions of the coil sections 10, 11, 14, 15 and 0 and this 'air is cooled and dehumidifed by contact with these coil sections in accordance with the conditionv ofthe control apparatus as hereinafter explained. Since only a portion of the air passing Athrough the v chamber 9 comes into intimate heat exchanging contact with active cooling surfaces, some ofthe air isl cooled to and below its/dewpoint whereas other portions ofthe air in kthe stream are cooled toa lesser degree. Thus, for example,vwhen the coil sections are at .a

temperature below the dewpoint of the entering air, a portion of this airis coold below its dewpoint and dehumidied by contact e with the active coil sections, while other portions of this air pass between the coils and accordingly retain considerable heat. The cooled and dehumidiiied air mixes with and is heated by the warmer air and accordingly, the air discharged from the chamber 9, although dehumidied to a certain extent, is nevertheless at a vcomfortable temperature well above saturation.

In leaving the chamber 9 all of the air.

passes through the eliminator plates 16, which act to remove all free moisture from the air.

The conditioned air is delivered to the enclosure 7 through the duct 22 and the used air is returned from thecenclos'ure through the duct 35. In order that the air in the enclo` sure'7 may be continuously replaced with fresh air, a certain proportion of the return air is expelled from the room through 'the duct 65, this amount of wasted air being made up from the fresh air entering the system through the duct 60. It will be appary.

ent that rather than discharge the air through a special duct, this air may be permitted to escape through the doors, windows or other v factors, itis necessary to dehumidify and cool the air supplied to the enclosure to a large extent. Under these conditions, the dry bulb thermostat; {i3-supplies a moderatey air pressure of say 7 lbs. per square inch to the operating diaphragms of the steam valve l25 and the mixing valve 39, maintaining the steam valve 25 closed As explained'above, j the spring 46 of the mixing valve 39 is strong enough vto maintain the gate42 of this' valve closed on its upper seat against this air'pre'ssure whereby all of the cooling liquid is passed through the cooler C and the lowestv obtainable liquid temperature' lis produced. The wet bulb thermostat or hygrostat 34 supplies a comparatively loin7 pressure of s ay 5 lbs. per uare inch to the operating dia-' phragms o the valves-7 2 through 76 whereby the valves 72, 73, 7 4'and7 5 are open'and the valve 76 is closed. Accordingly, some of the air in the stream passing through the chamber 9 comes into intimate contact with the cool i its dewpoint and dehumidied, while other `portions of the air in theH stream are cooled surfaces of the active coil sections 11, 14 and 15 and some of this air is cooled below of these valves and reducing the number of'v cooling coil sections which are active. The decrease in the number of the active cooling coil sections reduces the vdehumidifying effeet and* also reduces the amount of heat removed from the air stream. As a consequence, the air temperature increases and the dry bulb thermostat 33 responds and increases the air pressure on the operating diaphragm of the'valve 39, thereby permitting some of the cooling-liquid to by-pass around the cooler C, and accordingly, raise the cooling liquid temperature. If this increase' in coolingvliquid temperature reduces the de' humidifying eiect too greatly, the wet bulb thermostat 34 again responds and opens more of valves 72 through 76 to supply cooling liquid to morevof the coil sections and increase the dehumidiying action.

Assume now that there is a decrease in the amount of heat supplied to the system due to a lowering of the outside tem erature or to a Thus,

decrease in' the amount of eat emanating from sources within 'the enclosure. The

bulb thermostat 33 immediately res onds to the lower temperature and reduces' e pressure o'n the operating diaphragms of the valves and 39. This reduction in the control air pressure permits the spring 46 of` the mixing valve 39 to close the gate 42 of this valve on its upper seat. The steam valve 25 is referably set to remain closed until after t e control air lpressurehas been reduced below the .value at which the gate 42 of the valve 39 engages its upper seat. the reduction in control air pressure from the dry bulb thermostat 33 permits the gate 47 of the steam valve 25 to rise to an intermediate point, admitting steam to the lr ter radiator 23, and the desired air teni'- rature is maintained. If the relative hu'- closure becomes too low because of the higher air temperature, the wet bulb thermostat 34 further increases the control air pressure on the diaphragms of the valves 72 through 7 6 and thereb reduces the number of active vcooling co' sections to limit to the desired @degree the dehumidifying action.

As the su p1 f hmm the system is fur. ther reduce t e dry bulb thermostat 33 responds and reduces the control` airrpressure to a point at which the steam valve 25 lis opened more widely and more heat is accordingly supplied to the treated air to.maintain the desired'temperature within the enclosure.

Itwill be understood that thewet Vbulb thermostat or hygrostat 34 automatically regulates the number of active coolingcoil sections and so automatically .maintains thel desired degree of dehumidification'4 in 'the cooler in accordance with conditions of humidity in the enclosure..

Due to the fact that air stream, as Well as the temperature of the cooling liquid, is variably controlled, the

range of the system as well as the rapidity of its .response to changing conditions materially increased. y 4 v If, because of a sudden increase in foutside air temperature or in the amount of-heat supplied from sources in the enclosure, the controlair pressure delivered by the drybulb thermostat 33 increases to an abnormal high 1value of say 14 lbs., the geltel 420i the valve .39 will be closed on its .lower s eat and all. of the cooling liquid willgbe recirculated.

Under these conditions, ,it is desirable t'o turn the dry bulb thermostat controlY air pressure to a reasonable value so that the'I desired cooling'eiect can be-maintained and the air temperature reduced., 4This is accomplished by the emergency relief valve R which, as explained above, vents the control air pipe 77 to the atmosphere when the pressure iii-this pipe reaches an-abnormally high value of..14

lbs. per square inch, the relief valvegremain- I ing open until the pressure in this. pipe has been reduced to approximately -7: lbs. per square inch. This reduction in control air the hat @changing relation between ,the cooling liquidand the' los pressure permits the gate-42 'of the mixing valve 39 to rise and engage itsupper seat,

thereby passing all of the cooling liquid C, coolingthe active coil.

through the cooler sections and reducing the temperature 'of the air stream.z This reductionin air stream temperature causes the dry bulb thermostat 33 to respondan'd reduce the control air Apiessure supplied thereby, whereby normal oper ating .coiaiditions are again maintain The term@atmos hei-ic conditions asemployed in the speci cation and claims herein, means v,conditions of ltem rature or relative t1h umidity or a combination of these condi- I ions. 2 midity .of the air withdrawnfrom ,the en- Although theinvention has disclosed in connection with a single air .conditioning er capacity or range of control variation is required, the temperature control of the coolpheric conditions in the enclosure.

lWe claim: 1. In an air conditioning system,1ncomb1.

' nation with an enclosure in which conditioned air is required, acooler chamber, means for passing all of the air to be supplied to the enclosure in a single stream through said chamber, a plurality of separate cooling coils each extending entirely across the cross section of said cooler chamber, separately controllablemeans for supplying `a refrigerating medium to each of said coils, means governed.

in accordance with changes in atmospheric conditions in said enclosure for variably controlling the temperature of said refrigerating medium and the number of coils to which the medium is supplied and means for supplying all of the air 'passing through said coolerv chamber to said enclosure.4

2. In anv air conditioningsystem, in comb ination with an enclosure in which conditioned air is required, a cooler chamber,

, means for passing all of the air to -be supplied l to the enclosure in a; single stream through said chamber, a plurality of separate 'cooling Y temperature of said refrigeratlng medium, 'means for vinsuring the refrigeration of said coils each extending entirely across the cross section of said cooler chamber, omeans governed in accordance with changes in atmos pheric conditions in the enclosure for selectively supplying a refrigerating-medium to different numbers of said cooling coils, means governed by atmos heric conditions in said enclosure for varia ly controlling the temperature of 4said refrigerating inedium and means for supplying all of theair passing through said cooler chamber to said enclosure.

3. In an air conditioning system, in combination with an enclosure in .which conditioned air is required,- a-"cooler chamber,

means for passing all of the air to be supplied to the enclosure in a single stream through said chamber, a plurality of separate cooling coils each extending entirely acrgss the cross section of said cooler chamber?, separately controllablemeans for supplying a refrig- 4erating medium to each of said coils, means governed in accordance with changes inthe temperature of the air in said enclosure for variably controlling the temperature of said refrigerating medium and means governed in accordance @vitlrchanges in atmospheric conditions in said enclosure for variably controlling the number of coils to which the refrigerating medium is supplied.

4. In an air conditioning system, in combination with an enclosure in which ,conditioned air is required, a cooler chamber,

means for passing all of the air to be supplied to the enclosure in a single-'stream 5. In an air conditioning system in conibination with an enclosure in which condi- 'tioned air is required, a cooler chamber,

means for lpassing .all of the air to be supplied to the enclosure inv a single stream through said chamber, a plurality of separate cooling coils each extending entirely across'the cross section of saidcooler chamber, .means governed inI accordance with vchanges inthe humidityfof the air in said enclosure for selectively supplying a refrigeratin'g medium to dilierent numbers of said cooling coils, means governed 1n accordance with c anges-in the tempera-ture of the airioo in said-enclosure for variably controlling the v medium to fa low temperature when the temics perature responsive means 4becomes unball sure in a single stream throughsaid chamber, a plurality of cooled surfaces extending across thecross section of said c oolerxcham-v ber'in the path of said air stream, means forselectively cooling said surfaces to a tem` perature below the dew-point of the air entering said chamber whereby a quantity of 'iin moisture iscondensed from the air, and

means for- 'selectivelyfreducing the total 4cooled surface area exposed 'to said air stream.'v while maintaining a suicient temperaturedilerence'between the cooled surfaces and thel entering air stream to condense a substantially unchanged quantityfof moisture from the air in said stream, whereby the amount of sensible heat abstracted from Ithe- 'air stream may be reduced while= the amount of heat abstracted from the air stream as latent heat of condensation is maintained substantially unchanged. l

7. In an air conditioning system, in com. bination with an enclosure in which conditioned air is used, a cooler chamber, means for passing air to be supplied to the enclosure in a sin le stream through said cham- A ber, a pluralit of cooled surfaces each extending entire y across the cross section of said cooler chamber in the path of said air stream, means for selectively cooling said surfaces to a temperature below the dewpoint of the air entering said chamber whereby a quantity of moisture is condensed from the air, and means governed in accordance with changes in atmospheric conditions in said enclosure for selectively reducing the total cooled surface area exposed to said air stream while maintaining a sullicient temperature difference between the cooled surfaces and the entering air stream to condense a substantially unchanged quantity of moisture from the air in said stream, whereby the amount of sensible heat abstracted from the air stream may be reduced while the amountof 'heat abstracted from the air stream as latent heat of condensation is maintained substantially unchanged.

8. In an air conditioning system, in combination with an enclosure in which conditioned air is used, a cooler chamber, means for passing air to be supplied to the encloV sure in a single stream through said chamv ber, a plurality of cooled surfaces each extending entirely across the cross section of said cooler chamber in the path of said air stream, means for selectively cooling said surfaces to a temperature below the dewpoint of the air entering said chamber whereby a quantity of moisture is condensed from the air, and means governed in accordance with changes 'in the humidity of the air in said enclosure for selectively reducing thel total cooled surface area exposed to said air stream while maintaining a sufficient temperature difference between the cooled surfaces and the entering air stream -to condense a substantially unchanged quantity of moisture from the air in said stream, whereby the amount of sensible heat abstracted from the air stream may be reduced while the amount of heat abstracted from the air stream as latent heat of condensation is maintained substantially unchanged.

Inl testimony whereof we aiix our signatures. v I

ALFRED D. KARR. KARL D. PERKINS. 

